Hackable? Perhaps. i had the same thought you did a few months back when i found a photo key chain for $10. unfortunately when i cracked it open, it was anything BUT hackable. Or, I suppose, for my purposes. The main electronics were just a big blob of potting epoxy, the LCD was tightly soldered to the tiny PCB, and gosh, even the USB connector was proprietary. Ultimately, I found, that if you have to use special software to transfer photos, there's a good chance the software won't be an attack vector either.

My ultimate issue was there simply weren't' any parts that had already had work performed with them. I had nobody elses shoulders to ride on, and well, my time isn't so free that I could take the time to reverse-engineer the thing.

NOW, don't let my experience darken your mood with the project. Those things are cheap. Dirt cheap. Pick one up, perhaps you will have a very different result from wht I did.

If this is not what you have:http://hackaday.com/2009/01/08/hacking-a-digital-picture-keychain/...then I would say "only proceed if you are having fun". But, if I remember right, even with this hack you are loading each image into flash before displaying it. If true, (1) it will be slow and (2) you may eventually ware out the flash. There are lots of kits out there that will get you up and running faster. But, yes, they are (about) a magnitude more expensive.